Motor-starting device



.lunev 12, 1928. 4, 1,673,546

E. c. BALLMAN MOTOR STARTING DEVICE Filed sept. 21. 1922 *d rg rg l 1.1 i? 5 @t ,v 5 I el il #"5 E 2, l af D T" l c n r l l l l l l l I l Oef/cfzaa r. 6 v a K Genfer of ,9a/a {1o/1.

Awe/MI [ww/v C. MUM/v) Patented June .12, 1925.

UNITED STATES PATENT QTFQELE EDWIN C. BALIMAN, F ST. LOUIS, MISSOURI, SSIGIIOR TO BAIJDR ELECTRIC' COL'BL PA'NY, OF ST. LGUIS, MISSOURI; A CORPORATION OF MISSOURI.

MOTOR-STARTING DEVICE.

Application :led September 21. 1922. Serial No. 589,725.

This invention relates Ato motor starting devices, and more particularly to such starting devices as are mounted upon the motor itself so as to be operable upon the change of speed ot' the motor. c

One ot the objects oi' this invention, therefore, is to provide a motor starting device embodying switching means in which the arcing at the point or' making and breaking a circuit may be contined to certain parts,

which may be renewed when worn.

Another object or' this invention is to provide such switching means in which the cir cuit maintaining parts will loe kept ltree from corrosion by arcin.

Another object of this invention is to provide cent-riugally operated switching means which shall operate reliably at a definite nio tor speed. V

Another object of this invention is to provide centriiugally operated switching means wherein the operating effort will increase after operation thereof commences.

Further objects will appear' from the def tail description taken in connection With the accompanying drawings, in which:

Figure l shows a view in elevation of a device embodying this invention;

Figure 2 is a section on line 2-2, Figure l;

Figure 3 is a detail in perspective showing the bridging Contact;

Figure 4 is a detail in perspective show ing the means for locking the contact spring; and

Figure 5 is a diagram illustrating the operation ot this device.

Referrin to the accompanying drawing, the device s own in Figure l is arranged for mounting on the rotor shaft l oi an electric motor, and comprises a disc 2 having a huh 3 and an outer peripheral ange 4f. Between the hub 3 and the flange il, therefore, an annular space is provided Within which the mechanism is housed.

Mounted on the inner side of the flange 4 at intervals around the periphery thereof and suitably insulated therefrom oy means 'of insulating strips 5 and Washers 6 in a Well lrnovvn manner, is a series of contact blocks 'i'. These loloclrs are fastenedY in place hy means of screws or other suitable Jlasten` ing devices 8 which also be used to conneet the circuit leads hy which the current lis carried to and from the hloclis 'i'.

linger notches i3 for easy manipulation.

The blocks i are arranged in pairs uniformly spaced about the rim i and between each pair, a column or rod 9 is mounted radially so as to traverse the annular' space between the huh and the rim d. This col- @e unin 9 passes through a suitable aperture in the rim l and has a bearing in thc huh as illustrated in Figure 2. Near the outer end or' the column 9 is a groove l() arranged so that when the column is in place, this groove will lie just within the rim el. A metallic locking piece ll is provided with a groove l2 adapted to lit the neck of the column vSi within the groove l0. After the column has been inserted, the locking piece li may be slipped into its place in the groove l0 and within the rini i, so as to retain the column in place, the centrifugal force of the column assisting to retain the locking piece in pia s 'i`he locking piece ll may bc provided i cover 2O serves also to retain the icchii g pieces ll.

Mounted to slide loosely upon the colunu 9 is a bridging contact lei having con -ct faces l adapted to engage the opposte faces or' the Contact block for inaintaiiv electrical circuitbetween said Mounted upon the Contact le is make and break contacts le. 16 are loosely mounted upon lier` on the Contact le and may he connes o said pins sy dexihle pig tails The cui tacts 16 are thus adapted to move reely 'with respect to the contact lei. Said contacts i6 are of sufficient length to extend beyond the Contact faces l5, so that when urged eut wardly by centrifugal force, the Contact will engage the biocks l? before the conta-c faces l5 come into engagement with bloclrs.

Mounted on and surrounding the column 9 is a compression spring 19 which hears at one end against the Contact 'le so as 'fr hold the same against the huh 3 and other end against the locking piece il ing also to hold said locking piece again; dislodgement. rlhe spring i9 Y is pronortionedso that its length when open or uncompressed 1viii be greater than the distance L, Figure Q, between the inside of the rim fi and the center of the shaift i. i.

ion o' definite speed as will be more particularly set foith hereinafter.

As many pairs of contact blocks 7 and Abridging contacts 14 with the above described accessories may be provided as there are circuits to be controlled by this device. In the accompanying drawing, three such circuits are indicated.

In operation, the circuits to be controlled are connected to the contact blocks 7 through the screws 8 as indicated above. lVlien the motor is at rest, the springs 19 will force the bridging contacts 14 inwardly against the hub 3 tothe vposition indicated in Figure 1. As the motor-attains speed, centrifugal force acting upon the contacts 14 and 16 will urge the same radially outwardly. The contacts 14 will be held against such centrifugal force by thepsprings 19 but the contacts 16 will be urged outwardly to lie fiat against the outside faces of the contacts 14 in such a position that their ends will extend beyond the faces 15. When such a speed is attained that the centrifugal force of the contacts 14 and their connected parts is suiiicient to overcome the pressure of the springs 19, the contacts will slide radially outward along the columns 9. During such progress, the contacts 16 will first come into engagement With the blocks 7, thereby making the circuit between pairs of said blocks. Thereafter the contact faces 15 will come into engagement with the blocks 7 for maintaining said circuits. As the faces l5 come into engagement with the blocks 7, the ends of the contacts 16 will slide outwardly along said blocks. The circuits so made will thus be maintained so long as the motor runs at the attained speed. lVhen the motor stops, the centrifugal force acting upon the contacts 14 will be reduced and at a certain speed, the pressure of the spring 19 will be suicient to overcome such force and the contacts 14 will be forced back again to the position shown in'Figure 1 and the circuits between the blocks 7 opened. During such movement, the faces 15 will break the contact with the blocks 7 before the contacts 16 disengage, so that any arcing which may take place upon breaking the contact will do so at a point on the block 7 removed from the points of engagement of the faces 15 so that a clean surface is always maintained for Vthe engagement of said faces 15. The pig tails 18 provide a. low resistance connection between tlie contacts 16 through the contact 14 so that upon making or breaking the circuit, all of the current will beconfined to a path through the contacts 16 as soon as the faces 15 disengage with the result that there will be no supplementary arcing at the faces 15 and these faces will be maintained smooth and in a good condition for maintaining the circuit.

Reference will be had to the diagram, Figyand forces are plotted as ordinates.

ure 5, in order to explain the action of this device. This diagram represents a plot of the forces acting upon the contacts 14 during operation. In this diagram, displacements along the column 9 are plotted as abscissae Thus the line OS represents the variation of the force of the spring 19 with deflection or compression along the column 9. Similarly the line GIV represents the variation of centrifugal force acting upon the weight 14 with its displacement along the column 9. Since the spring 19 has a greater length than the distance L as previously explained, said spring will have an initial deflection represented by OA in the diagram and will consequently exert an initial pressure represented by OC. The `diagram represents conditions obtaiuing at that particular speed of the rotor at which the centrifugal force of the contact 14 is just equal to the pressure exerted by the spring 19. This centrifugal force will, therefore, also be represented by OO. 'This centrifugal force corresponds to a displacement of the contact 14 from the center of rotation equal to GA. Now as the contact 14 moves outwardly under the action of centrifugal force, the centrifugal force acting thereon will increase along the line GIV, while the resisting pressure of the spring 19 will increase along the line OS, so that when the contact 14 comes into engagement with the block 7, a new position cor-'- responding to the position B on the diagram will have been attained. In this position the centrifugal force represented by OE will y be greater than the spring pressure 4represented by OD. This shows that the centrifugal effort moving the contact 14 increases With the displacement of said contact along the column 9 more rapidly than does the spring resistance thereto. A desirable result obtained by this arrangement is that as soon as the contact 14 begins to move under the action of centrifugal force, said movement will accelerate and the circuit will be closed with a decided snap of the contact 14 against the blocks 7. This is a desirable result for the reason that it makes for positive contact and cuts down arcing to a minimum.

It will thus be seen that this invention accomplishes its objects. A circuit closing device is provided in which the contact maintaining faces will always be kept in a clean and smooth condition on account of the fact that arcing is definitely coniinedlto the auxiliary contacts 16.v The mechanical action of this device will always be positive and take place at a definite speed by virtue of the action explained in connection with Figure 5. Thus, the so-called creeping of the contacts to contacting position is entirely avoided. Y

' It is obvious that various changes may be made in details of construction without departing from the spirit of this invention; it is, therefore, to he understood that this invention is not to be limited to the specific details shown and described.

Having thus described the invention, what is claimed is:

l. In a machine of the character described, a centrifugal switch, comprising, a series of main contacts, a relatively movable contact centriiugally operable to bridge certain ot said main contacts, and an auxiliary contact loosely mounted on said movable contact and having a low-resistance flexible connection therewith.

2. In a machine of the character described, a centrifugal switch, comprising, a series of main contacts, a relatively movable contact centrifugally operable to bridge certain of said main contacts, an auxiliary Contact loosely mounted on said movable Contact and extending tlierebeyond so as to engage said main contact in advance of said movable contact, and a low-resistance flexible connec` tion between said auxiliary contact and said movable contact.

3. In a machine of the character: described, a centrifugal switch, comprising, a series of main contacts, a relatively movable contact centritugally operable to bridge certain of said main contacts, and an auxiliary contact loosely mounted on said movable Contact and centrifugally operated to make and break contact with said main Contact.

4. In a machine of the character described, a centrifugal switch, comprising, a casing,

a series of main contacts within said casing, a centrifugally operated bridging Contact adapted to engage certain of said main contacts, a guide rod for said bridging Contact arranged to slip into said casing, a spring supported by said rod and adapted to restrain said bridging contact, and a lock for said rod abutting said casing on the inside thereof.

5. In a machine ofthe character described, a centrifugal switch, comprising, a casing, a series of main contacts within said casing, a centrifugally operated bridging contact adapted to engage certain of said main contacts, a guide rod for said bridging contact arranged to slip into said casing, a spring supported by said rod and adapted to restrain said bridging contact, and a lock for said rod abutting said casing on the inside thereof, and retained in such abutment by said spring. y

6. In a machine of the character described, a centrifugal switch, comprising, a casing, a series of main contacts within said casing, a centrifugally operated bridging contact adapted to engage certain of said main contacts. a guide rod for said bridging contact arranged to slip into said casing, a spring supported by said rod and adapted to restrain said bridging contact, a lock for said rod abutting said casing on the inside thereoi', and a cover for said casing enclosing said lock.

In testimony whereof I affix my signature this 80th day 0I" August, 1922.

EDWIN C. BALLMAN. 

